Anjani Ganase brings the latest biodiversity news: warning that systems are collapsing from the poles to the tropics; and that human intervention can make a difference.
The tale of vanishing snow crabs
In Alaska, the snow crab harvest in October was cancelled suddenly over fears of a crash in the snow crab population in the Bering Strait. The sudden drop in population came as a surprise to both fisherfolk and scientists alike, after the booming population of over 11 billion crabs surveyed in 2018 as part of the annual shellfish assessment programme done by the Alaska Fisheries Science Centre, NOAA.
The snow crab population in 2018 - was this the first warning? - was way above average but by 2019, the number dropped to half the amount; and by 2021 fewer than 940 million crabs remained. This is a loss of over 91 per cent of the population over three years. Scientists couldn't quite understand it, so in 2022 they surveyed again but covered a larger area including farther north and west, closer to Russian territory. Such a sudden and enormous loss in population is known as a mass mortality event and is likely related to climate change. Ocean temperatures in the polar regions have been heating up at a much faster rate compared to other parts of the world. The typical temperature of snow crab habitats is about 1.3 C, but since 2016, the average ocean temperature shot up to 3.5 C, way above the norm.
Scientists speculate that the higher temperatures may have permitted ocean predators from warmer areas to invade and prey on the snow crabs. Other theories purport that limited food resources (possibly through ocean warming) incapable of sustaining the large crab population resulted in the population crash. For an industry that brings in about US$200 million in revenue annually, the crash is devastating, especially as other fishing industries, including halibut, cod and pollock, have been lost to overfishing, disasters such as the Exxon Valdez oil spill and global warming.
Adapting to avoid extinction
Paleontologists (scientists who study ancient ecosystems through fossils) comparing modern day populations of megafauna (large animals) in forested south east Asia with ancient populations have noted that a handful of species are defying the trend to extinction. Human development typically results in 'trophic downgrading' of surrounding areas, which means there is the loss of large animals, typical apex predators, because of over exploitation, diminishing prey or habitat loss that may have cascading ecological consequences. One example is the loss of top predators - sharks, groupers - on coral reefs.
Scientists instead found that although many large animals were dwindling in numbers in present day Asian forests, there is a handful of large animals with increasing populations, especially close to urban areas. In particular, four animals - tigers, Asian elephants, wild boars and clouded leopards - have larger populations closer to urban centres because of human champions against poaching in natio
